It is well known that the achievement of a high percentage rate of germination capacity, high speed of germination of seeds, and development of a healthy, strong bud are dependent on, inter alia, the chemical composition, the biological, microbiological and physicochemical properties of the surrounding soil or another plant growth medium, or in the case of the pelletization of seeds, on the properties of the pellet.
There have been publications on the effects of different cations and anions on the stimulation of the germination capacity of seeds, such as KNO3, ethylene glycol, and others. In addition, information about the effect of pH of the environment on the course of the germination capacity of seeds has been reported. The positive effect of chemical and biological protection of seeds against moulds, bacteria and viruses on the germination and development of the germ is also known for long.
The temperature and humidity of the environment of a seed are among the factors known to significantly influence the course of germination. Successful germination depends heavily on the sufficient supply of oxygen to the seed, and on the other hand, on the rapid elimination of the gaseous products of metabolism or chemical or biological reactions of bacterial origin.
Thus far, modifications of the properties of soils and pellets aimed at achieving sufficient humidity and oxygen supply, including the transport of gaseous products during the germination process, have been oriented in particular towards the preparation of new, or the modification of existing, raw material composition of the pelletization mixtures or soils. Pelletization mixtures typically comprise various types of organic or inorganic fibers, clays and inert inorganic materials, and contain also particles with internal open porosity. Other frequently used types of pelletization mixtures are various combinations of clays with inert raw materials without the addition of fibers. The combination of raw materials with different water sorption properties is often used to modify and adjust the overall capacity of the pellets to absorb water. The fibers, together with the other raw materials, form the texture of the pellet with open porosity, which determines, along with the water absorption rate of the pellet, the pellet's capacity for the transport of the gaseous phase. The mode of transport of the water by these pellets is determined by the gradual imbibition of water from the external surface of the pellet throughout its depth up to the seed. This is caused by the imbibition capacity of the particles contained in the raw materials, along with the capillary suction of water in the open pores of the pellet's structure. It is believed that the clay constituents of the pelletization mixture are responsible for the cohesion of particles contained in the raw materials during the pelletization of seeds. At the same time, clay constituents are added to increase the mechanical strength of a pellet after drying. Especially when using a mechanical type of sowing, the mechanical strength of seed pellets is important. Inorganic binders, such as gypsum, can be added to the composition of the pellet, to adjust the mechanical strength of the pellet. In other cases, various types of glues, most frequently cellulose-based glues such as carboxymethyl cellulose, are used. Experiments with the addition of polyacrylates, silicones, polyvinyl alcohol and other types of organic/polymeric substances have also been performed. The disadvantage of the use of these systems in agriculture and forestry can include the long-term stability of the said substances in nature. Excess application thereof may represent a high ecological burden for the nature.
To date, the pelletization of seed has been performed in most cases in pelletizers by adding water and pelletization mixture. A pelletizer refers to an industrial apparatus for the production of pellets. The raw material composition of the pelletization mixture, especially the content of clays and admixture of organic glues, controls the speed of pelletization of seeds and the yield of pellets of the required size after pelletization. It is well known that the pelletization process can be controlled by the size of the respective doses of the pelletization powder and water, by the time of pelletization per dose and by the speed of revolutions of the pelletizer. An important feature of this process is allowing sufficient time for the addition of water and pelletization mixture to achieve a sufficient soaking of the raw materials contained in the product with the water, especially in the case of clay materials, to achieve a binding of the particles of the mixture and the adhesion thereof to the seed surface or to a previously pelleted layer. The speed of mixing and adhesion is a limiting factor of the total pelletization time and homogeneity in the properties of pellets. Further, the pellet must be understood, for its manufacture and use according to the invention, to be of any suitable shape or form, e.g., a tablet, a strip or any other form suitable for transport and/or sowing of seeds.
Similar principles for the modification of properties of the pellets are used for the modification of soils. For example, the permeability of water and gases in heavy clay soil can be improved by the addition of inert raw materials (such as sand, ashes, diatomaceous earth, and others) or fibers (such as straw) to the clay soil. In contrast, the addition of clays, for example, may be used to increase the water absorption capacity in light sandy soils.
Known procedures for improving the properties of pellets and soils generally involve the combination of various types and relative proportions of fibrous materials, clays, and inert raw materials, with the potential addition of organic glues. Combinations of raw materials are used to control the final properties of the pellets and soils which, in turn, determine the transport of water and oxygen, or gas in general, by the pellet.
However, the production of pellets and soils according to existing methods is frequently hampered by the fact that improvement of one property is often associated with the impairment of another property. For example, the increase in the mechanical strength of the pellet by means of an increased content of clay in the mixture frequently results in the compaction and reduced open porosity of the pellet, thus causing an impairment of the conditions for the transport of the gaseous phase by the pellet and increased resistance of the pellet for the growth of the germ. Another example is the increased porosity of the pellet achieved by the increased content of fibers and porous particles of the inert raw material in the mixture. This modification can result in the increased absorption of water by the pellet, accompanied by the reduced germination capacity of the seeds, especially in humid climatic conditions with excess moisture. The increase in the mechanical strength of the pellet by the significant addition of, for example, carboxymethyl cellulose is frequently associated with the proneness of the pellet to the growth of moulds in humid environments. The modification of the mechanical strength and absorption properties of the pellets with respect to water achieved by adding e.g., polyacrylates, can be accompanied by the increased resistance of the pellet for the growth of the germ, given the stability and irreversible change of the dried polyacrylate in moist conditions.